Hunger is a problem faced by many people all over the world, and as the population grows, so does the need for food such as cereals. Because of this, the need for food with higher protein and nutrient content will be increasingly important. NAM-B1, a NAC-protein gene in wheat, has been shown to control the grain protein content and nutrient values, as well as senescence. In barley, two orthologous genes have been found, HvNAM1 and HvNAM2. This study focuses on Nordic barley accessions and how haplotypes of HvNAM1 and HvNAM2 correlate to the grain protein content (GPC) and nutrient content. No correlations between the different haplotypes of the HvNAM genes and the nutrient content and GPC were found. No differences in nutrient content and GPC were found in Nordic accessions originating from Sweden, Norway, Finland, or Denmark, nor were differences found for improvements status groups or for six-row barley and two-row barley. The Nordic accessions were shown to generally have high GPC when compared to control groups Karl and Lewis. However, even if the results of this study indicate that the HvNAM genes do not have major effects on the nutrient contents or GPC, Nordic barley might still be good material for plant improvement. Other factors such as other genes, environmental effects, and gene expression should therefore be investigated.

The effects of soil nutrient status on the performance of four South African wheat genotypes were investigated in a long-term fertilization experiment. The objective was to quantify the effects of soil fertility on yield, yield components, grain nitrogen content, grain protein yield, grain protein content, flour yield and bread-making quality. The relative contribution of main stems and tillers, as well as the contribution of first, second and third kernels in the spikelets to grain yield and grain protein content were determined. The interactive effects between photoperiod, temperature and vernalization on grain yield, yield components and grain protein content were also quantified. Increasing soil fertility increased grain yield and most components of yield, grain nitrogen content, grain protein yield, aboveground biomass and harvest index, but depressed mean kernel mass. Significant interactions between cultivar and soil fertility were observed for grain yield, grain number, kernel mass, protein yield, biomass and harvest index, indicating differences in cultivar ability to produce yield and quality. Within a cultivar, the main stem, first tiller and second tiller did not differ in mean grain protein content, indicating that late-maturing tillers do not affect the grain protein content of wheat. Grain protein content, flour yield, loaf volume, water absorption and mixograph peak mixing time varied with soil fertility. The interaction between cultivar and soil fertility was significant for the above mentioned parameters with the exception of mixograph peak mixing time, indicating wheat genotypes differences in bread-making quality potential. The potential ability of wheat cultivar Kariega to produce higher grain yield, protein yield and loaf volume in the K and P limiting soil fertility situations deserve further investigation. In a growth chamber study, the low temperature regimes and long photoperiod conditions resulted in the highest grain yield, number of grains, largest mean kernel size and highest grain protein content. / Dissertation (PhD)--University of Pretoria, 2003. / Plant Production and Soil Science / unrestricted

Grain protein content (GPC) in wheat has been found to be regulated by the gene NAM-B1. Homologues to the NAM-B1 gene have been found in barley, HvNAM-1 and HvNAM-2. Previous studies have found that base mutations in the NAM-1 gene at base position 544 might have an impact on GPC. Previous studies also found that landrace of barley showed higher GPC than cultivated barley, indicating that plant improvement might have affected base mutations and therefore GPC. I wanted to study if there are any nutritional differences in Nordic barley and if those differences might correlate with haplotypes. Comparisons of barley varieties from four Nordic countries, and two varieties from the US used as low and high GPC controls, did not show any significant differences depending on their origin country and no differences regarding plant improvement status between the countries. When sequencing Nordic barley varieties, five haplotypes were found for the gene HvNAM-1, and two haplotypes for the gene HvNAM-2. A low polymorphism for both genes indicate a strong natural selection for the consensus haplotype which might be preferable for Nordic climate with a short growing season and cold temperatures. Even though it is not clear what is the cause of the low polymorphism in Nordic barley varieties, they showed a generally higher nutrient content than barley varieties of the high GPC and may be suitable for breeding for a yield with a high nutrient content.

Rice is an important human staple food for over half of the world’s population. Amylose content (AC), gelatinization temperature (GT), grain protein content (GPC), percentage grain chalkiness (PGC), and mineral content are important parameters for evaluating rice quality, which attracts customers and breeders. Only limited genes or QTLs (OsAAP6, OsGluA2, OsASN1, Chalk5, OsHMA3, etc.) are reported regulating rice GPC, PGC, and mineral content due to the lack of genetic knowledge and molecular markers. To dissect the genetic architecture of rice grain quality regulation, genome wide association studies (GWAS) were performed using two populations (USDA-mini core collection and a panel of 662 rice accessions from the 3K Rice Genomes Project). A total of 28, 11, 4, 3, 40, 3, 4, 3, and 10 QTLs were identified associated with Cd, Co, Cu, K, Mo, Ni, Rb, Sr, and Zn under flooded environment, while, 23, 7, 7, 7, and 3 QTLs were detected to be associated with Cd, Fe, Mo, Ni, and Zn under unflooded environment, respectively. Moreover, 6, 5, and 2 significant QTLs were tightly associated with kernel length, kernel rate, kernel width, respectively. Furthermore, 44, 7, 27, and 20 QTLs were identified associated with AC, GT, GPC, and PGC, respectively. Overall, 53 (~ 20.08%) of the 264 QTLs were coinciding with previously reported QTLs/genes, and 211 (~ 79.92%) were novel QTLs. A candidate gene, OsPCAT (putative cationic transporter), associated with GPC in the dry season was selected for further analysis. The OsPCAT gene belongs to the amino acid transporters (AATs) family with nine closely related members reported in Oryza Sativa. The classification and evolution of the CAT family (a subgroup of AATs family) using 61 species were studied. The over-expression lines (OsPCAT-OX) and CRISPR-Cas9 knock-out lines (OsPCAT-KO) were developed to study the function of OsPCAT gene. The preliminary results showed the GPC in OsPCAT-OX lines was increased and OsPCAT-KO lines were decreased compared to WT. Overall, a large number of new and reported QTLs associated with rice grain quality have been identified. This work lays the foundation for marker development in breeding and further investigation on rice grain quality regulation.

Les associations d'espèces sont définies comme la culture simultanée d'au moins deux espèces sur la même parcelle pendant une période significative de leur croissance. Ce système permettrait d'améliorer l'utilisation des ressources du milieu (eau, azote, lumière…) et ainsi d'augmenter le rendement et la qualité des grains par rapport aux cultures monospécifiques. L'objectif de notre travail était d'analyser le fonctionnement et d'évaluer la performance des associations blé dur - pois d'hiver et blé dur - féverole d'hiver pour aider à la conception d'itinéraires techniques adaptés à différents objectifs de production. Pour cela nous avons testé, au cours de trois années d'expérimentations, différentes combinaisons de variétés de blé dur, disponibilités en azote, structures de couverts et densités de plantes. Nos résultats ont confirmé l'intérêt de ces systèmes pour améliorer le rendement et la teneur en protéines du blé dur comparativement aux cultures monospécifiques mais également pour la réduction des ravageurs, maladies et de l'enherbement dans certaines conditions. Ces systèmes sont ainsi particulièrement bien adaptés aux situations à faible disponibilité en azote en raison de la complémentarité entre céréale et légumineuse pour l'utilisation de l'azote (minéral du sol et fixation symbiotique) mais aussi pour la captation de l'énergie lumineuse. In fine, ce travail a permis de proposer des prototypes d'itinéraires techniques d'associations adaptés à différents objectifs de production, grâce notamment à l'analyse dynamique des compétitions et complémentarités entre espèces au sein du couvert et en particulier de l'élaboration du rendement du blé dur en association. / Intercropping is the simultaneous growing of two or more species in the same field for a significant period. Such systems are known to use available resources (water, light, nitrogen…) more efficiently than their corresponding sole crops and consequently to increase yield and grain protein concentration particularly in low N input systems. The aim of our work was to analyse the functioning of durum wheat - winter pea and durum wheat - winter faba bean intercrops. A 3-year field experiment was carried out with different fertilizer-N levels, wheat cultivars and plant densities. The intercrop efficiency was studied in order to further design low inputs cropping systems for specific objectives. Our results confirm that intercropping is more suited to low-N-input systems because it takes advantage of complementary N sources (soil mineral N and N2 fixation) and light use between species of the intercrop. Thus, intercrops were more efficient than sole crops for yield, they increased durum wheat grain protein concentration and in certain cases reduced weeds, pests and diseases. Finally, our work indicates that intercrops can be optimized for specific objectives by the choice of crop species, cultivars, N fertilization and plant densities in order to maximize resource capture and minimize competition. Indeed, intercrop efficiency is determined by the complementary resource use between the two species as well as the relative strength of the intra- and interspecific dynamic competitive interactions.